Current switch circuits may be utilized in a plurality of applications, for example, in charge pumps for use in phase locked loops and delay locked loops. Typical current switch circuits include an N-type differential transistor pair with a known current being steered out of an output wherein this output may then be coupled to drive a loop filter. In general, the dynamic range of the charge pump is limited by the current switch wherein the dynamic range is limited by the differential transistor pair non-linearity (i.e. saturation). This typically amounts to approximately a three V.sub.BE voltage limitation. Thus, the dynamic range of typical current switch circuits have limitations for low operating supply voltages.
In order to combat this problem when operating in a phase locked loop application, the voltage controlled oscillator on the other side of the loop filter needs to have a high gain in order for the phase locked loop to cover a large frequency span. However, this increases the noise sensitivity of the system.
Hence, there exists a need for an improved current switch circuit for operating at low supply voltages while not compromising dynamic range.